METHOD AND BASE STATION FOR TRACKING POWER PEAKS OF A SIGNAL

Description

TECHNICAL FIELD

[0001] The present invention relates to radio access networks, and, more particularly, to systems and methods for tracking a signal from a mobile terminal.

BACKGROUND

[0002] In order to maintain air interface synchronization between a terminal (e.g., a mobile phone) and a base station, as well as to demodulate a radio signal transmitted by the terminal, the base station typically uses a tracking mechanism to follow the paths of a signal transmitted by the terminal. The tracking mechanism typically tracks the terminal within a defined timing window.

[0003] During initial access between a terminal and a base station, or when handing off a terminal connection from one base to another base station, the base station to which the connection is being made typically searches for signal paths associated with the terminal over the entire range of the base station. After the base station finds a signal path, the base station tracks the terminal by searching a much smaller timing window than was used to initially locate the terminal.

[0004] US 6 006 096 A discloses a method for locating a mobile terminal in a cellular network, wherein at least two base stations locate a terminal while stepwise decreasing the size of their respective search areas.

[0005] In some radio access networks, a "reflected" signal could be stronger than a direct signal. For example, a signal transmitted from a repeater or relay or a signal bouncing off of a mountain or other structure may be stronger than the original signal transmitted by the terminal. Typically, there is a large timing difference between the direct signal and the reflected signal.

[0006] Using the repeater case as an example, a terminal moving away from the base station towards the repeater is tracked by the base station to maintain air interface synchronisation. At some point, from the base station's perspective, the strength of the signal received from the repeater will be larger than the strength of the signal received directly from the terminal. The timing difference is usually large between the direct signal being tracked and the "reflected" signal (i.e., the signal transmitted by the repeater). If the timing difference is larger than can be handled by the tracking mechanism and its window size, the base station tracking mechanism will not be able to include the stronger signal from the radio repeater. The strong signal from the radio repeater will instead contribute to the received noise, and reduce the signal to noise ratio.

[0007] What is desired are systems and methods for overcoming the problem of tracking the signal from a terminal, in scenarios when there is a large timing difference between a reflected signal and the direct signal from the terminal.

SUMMARY

[0008] In one aspect, the invention provides a method for tracking a signal from a mobile terminal and to find multipath signals that are outside a current timing window. In some embodiments, this method includes the following steps: receiving a signal transmitted from the mobile terminal; searching a primary timing window for a signal associated with the mobile terminal; searching a secondary timing window for a signal associated with the mobile terminal, wherein the secondary timing window is larger than the primary timing window; determining the strength of a signal associated with the mobile terminal that was found by searching the secondary timing window; determining whether the primary timing window should be modified based on the determined strength of the signal that was found by searching the secondary timing window; and modifying the primary timing window in response to a determination that the strength of the signal that was found by searching the secondary timing window exceeds a threshold (e.g., exceeds the strength of a signal associated with the mobile terminal that was found by searching the primary timing window or other threshold). Both the primary timing window and the secondary timing window may be searched periodically (i.e., at regular or irregular time intervals) and, in some embodiments, the secondary timing window is searched less frequently than the primary timing window.

[0009] In some embodiments, the step of modifying the primary timing window comprises altering the primary timing window so that the primary timing window includes the location (in time) where the signal associated with the mobile terminal was found in the secondary timing window. In some embodiments, the primary timing window is so altered without changing the size of the timing window.

[0010] In some embodiments, the step of modifying the primary timing window comprises increasing the size of the primary timing window, wherein the size of the primary timing window is increased so that the new primary timing window includes the location (in time) where the signal associated with the mobile terminal was found in the secondary timing window and the location (in time) where a signal associated with the mobile terminal was found in the old primary timing window.

[0011] In some embodiments, the step of modifying the primary timing window comprises creating a second primary timing window, wherein the second primary timing window is smaller in size than the secondary timing window but includes the location (in time) where the signal associated with the mobile terminal was found in the secondary timing window. In these embodiments, the method may further include the step of continuously searching, for some period of time, the first and second primary timing windows for a signal associated with the mobile terminal.

[0012] In some embodiments, the method may further include the step of sending a timing alignment value to the mobile terminal in response to a determination that the strength of the signal that was found by searching the secondary timing window exceeds a threshold, wherein the timing alignment value corresponds to a delay associated with that signal.

[0013] In another aspect, the present invention provides an improved base station. In some embodiments, the improved base station includes: a receiver for receiving signals transmitted from a terminal; a terminal tracking module configured to search a primary timing window for a signal associated with the terminal; a secondary searching module configured to search a secondary timing window for a signal associated with the terminal, wherein the secondary timing window is larger than the primary timing window; a signal strength determining module configured to determine the strength of a signal associated with the terminal that was found by searching the secondary timing window; and a data processing module configured to determine whether the primary timing window should be modified based on a determined strength of the signal that was found by searching the secondary timing window.

[0014] In some embodiments, the terminal tracking module is further configured to modify the primary timing window in response to receiving information indicating that the strength of the signal that was found by searching the secondary timing window exceeds a threshold.

[0015] In some embodiments, the terminal tracking module is configured to modify the primary search in response to receiving said information by (1) altering the primary timing window so that the primary timing window includes the location (in time) where the signal associated with the terminal was found in the secondary timing window without increasing the size of the timing window, (2) increasing the size of the primary timing window so that the new primary timing window includes the location (in time) where the signal associated with the terminal was found in the secondary timing window and the location (in time) where a signal associated with the terminal was found in the old primary timing window, and/or (3) creating a second primary timing window.

[0016] In some embodiments, the base station may also include a timing module configured to send a timing alignment value to the terminal in response to a determination that the strength of the signal that was found by searching the secondary timing window exceeds a threshold, wherein the timing alignment value corresponds to a delay associated with that signal.

[0017] In some embodiments, the secondary searching module is configured to search the secondary timing window less frequently than the tracking module is configured to search the primary timing window.

[0018] The above and other aspects and embodiments are described below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments of the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. In the drawings, like reference numbers indicate identical or functionally similar elements.

[0020] FIG. 1 illustrates a portion of a communication network according to some embodiments.

[0021] FIG. 2 is a flow chart illustrating a process according to some embodiments of the invention.

[0022] FIG. 3 is a functional block diagram of a base station according to some embodiments of the invention.

[0023] FIG. 4 is a functional block diagram of a base station tracking system according to some embodiments.

DETAILED DESCRIPTION

[0024] Referring now to FIG. 1, FIG. 1 illustrates a portion of a communications network 100 according to some embodiments of the invention. Network 100 includes a terminal (a.k.a., terminal equipment (TE)) in direct communication with a base station 104 and in indirect communication with the base station through a repeater 106 (or relay). As illustrated in FIG. 1, TE 102 transmits a signal 110. Signal 110 is received by base station 104 and repeater 106. Repeater 106 transmits a signal 112 corresponding to signal 110. Signal 112 is also received by base station 104.

[0025] As described in the background section, base station 104 includes a tracking mechanism to track TE 102. In some embodiments, base station 104 tracks TE 102 by searching a determined window for signal peaks associated with TE 102. As also described in the background section, "reflected" signal 112 could be stronger than direct signal 110. This could be the case, for example, when the repeater 106 is positioned between TE 102 and base station 104. If the timing difference between direct signal 110 being tracked and "reflected" signal 112 is larger than can be handled by the tracking mechanism and its window size, the base station will not be able to include signal 112 from the radio repeater. Signal 112 from repeater 106 will instead contribute to the noise received at base station 104, and, thereby, reduce the ratio of the level of signal 110 to the level of received noise.

[0026] To overcome this problem, base station 104 can be configured to perform process 200 shown in FIG. 2. Process 200 may begin in step 202, where base station 104 receives a signal transmitted by TE 102. In step 204, a TE tracking module is configured to track the signal from TE 102 by searching, for some period of time, at least one primary timing window for a signal (e.g., a signal peak) associated with TE 102.

[0027] In step 206, base station 104 searches a secondary timing window for a signal (e.g., an indirect signal) associated with TE 102, where the secondary timing window is larger than the primary timing window. In some embodiments, the secondary timing window is searched less frequently than the primary timing window. For example, the primary timing window may be searched continuously, while the secondary timing window may be searched once per second.

[0028] In step 208, if a signal associated with TE 102 is found as a result of searching the secondary timing window, information pertaining to the signal is provided to the TE tracking module. In step 210, in response to receiving the information pertaining to the signal that was found as a result of searching the secondary timing window, the base station tracking module modifies the primary timing window by, for example, performing one or more of steps 212a-212d.

[0029] In step 212a, the tracking module alters the primary timing window so that the primary timing window includes the location (in time) were the signal associated with TE 102 was found as a result of searching the secondary timing window. In some embodiments, the act of altering the primary timing window does not change the size of the primary timing window. In some embodiments, the altering may be done with hysteresis, to avoid frequent tracking changes due to fluctuations when both signals have approximately the same strength. This hysteresis could be in time as well as the signal strength

[0030] In step 212b, the tracking module increases the size of the primary timing window so that the new primary timing window includes the location (in time) where the signal associated with TE 102 was found in the secondary timing window and the location (in time) where the signal associated with TE 102 was found in the old primary timing window.

[0031] In step 212c, the tracking module continuously searches not only the primary timing window but also another timing window (i.e., a second primary timing window), where the second primary timing window is smaller in size than the secondary timing window but includes the location (in time) where the signal associated with TE 102 was found in the secondary timing window.

[0032] In step 212d, base station 104 transmits to TE 102 a timing alignment value in response to determining that the strength of the signal that was found by searching the secondary timing window exceeds a threshold, wherein the timing alignment value corresponds to a delay associated with that signal.

[0033] In the above manner, base station 104 will be able to use the "reflected" signal, and, thus, the reflected signal will not add to the noise level.

[0034] Referring now to FIG. 3, FIG. 3 is a functional block diagram of base station 104 according to some embodiments of the invention. As shown, base station 104 may comprise a data processing system 302 (e.g., one or more microprocessors), a data storage system 306 (e.g., one or more non-volatile storage devices) and computer software 308 stored on the storage system 306. Configuration parameters 310 may also be stored in storage system 306. Base station 104 also includes transmit/receive (Tx/Rx) circuitry 304 for transmitting data to and receiving data from TE 102 and transmit/receive (Tx/Rx) circuitry 305 for transmitting data to and receiving data from, for example, a core network 333.

[0035] Software 308 is configured such that when processing system 302 executes software 308, base station 104 performs steps described above with reference to the flow chart shown in FIG. 2. For example, software 308 may include: (1) a terminal tracking module 402 (see FIG. 4) configured to search, for some period of time, a primary timing window for a signal associated with the terminal; (2) a secondary searching module 404 configured to search a secondary timing window for a signal associated with the terminal, wherein the secondary timing window is larger than the primary timing window; (3) a signal strength determining module 406 configured to determine the strength of a signal associated with the terminal that was found by searching the secondary timing window; and (4) a data processing module 408 configured to determine whether the primary timing window should be modified based on a determined strength of the signal that was found by searching the secondary timing window.

[0036] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but by the appended claims.

Claims

1. A method of operating a base station (104) to track a mobile terminal (102), the base station carrying out the following steps:

receiving a signal transmitted from the mobile terminal (102);

searching a primary timing window for a signal associated with the mobile terminal;

searching a secondary timing window for a signal associated with the mobile terminal, wherein the secondary timing window is larger than the primary timing window;

determining the strength of a signal associated with the mobile terminal that was found by searching the secondary timing window; and

determining whether the primary timing window should be modified based on the determined strength of the signal that was found by searching the secondary timing window.

2. A method according to claim 1, further comprising modifying the primary timing window in response to a determination that the strength of the signal that was found by searching the secondary timing window exceeds a threshold.

3. A method according to claim 2, further comprising modifying the primary timing window in response to a determination that the strength of the signal that was found by searching the secondary timing window exceed the strength of a signal associated with the mobile terminal that was found by searching the primary timing window.

4. A method according to claim 2 or 3, wherein the step of modifying the primary timing window comprises altering the primary timing window so that the primary timing window includes the location, in time, where the signal associated with the mobile terminal was found in the secondary timing window.

5. A method according to claim 4, wherein the size of the primary timing window is increased so that the new primary timing window includes the location, in time, where the signal associated with the mobile terminal was found in the secondary timing window and the location, in time, where a signal associated with the mobile terminal was found in the old primary timing window.

6. A method according to claim 2 or 3 , wherein the step of modifying the primary timing window comprises creating a second primary timing window, and the method further comprises continuously searching, for some period of time, the first and second primary timing windows for a signal associated with the mobile terminal, wherein the second primary timing window is smaller in size than the secondary timing window but includes the location, in time, where the signal associated with the mobile terminal was found in the secondary timing window.

7. A method according to any preceding claim, further comprising:

sending a timing alignment value to the mobile terminal (102) in response to a determination that the strength of the signal that was found by searching the secondary timing window exceeds a threshold, wherein the timing alignment value corresponds to a delay associated with that signal.

8. A method according to any preceding claim, wherein the secondary timing window is searched less frequently than the primary timing window.

9. A base station (104), comprising:

a receiver (304) for receiving signals transmitted from a terminal (102);

a terminal tracking module configured to search a primary timing window for a signal associated with the terminal;

a secondary searching module configured to search a secondary timing window for a signal associated with the terminal, wherein the secondary timing window is larger than the primary timing window;

a signal strength determining module configured to determine the strength of a signal associated with the terminal that was found by searching the secondary timing window; and

a data processing module configured to determine whether the primary timing window should be modified based on a determined strength of the signal that was found by searching the secondary timing window.

10. A base station according to claim 9, wherein the terminal tracking module is further configured to modify the primary timing window in response to receiving information indicating that the strength of the signal that was found by searching the secondary timing window exceeds a threshold.

11. A base station according to claim 10, wherein the threshold value is a value representing the strength of a signal associated with the terminal that was found by searching the primary timing window.

12. A base station according to claim 10 or 11, wherein the terminal tracking module is configured to modify the primary timing window in response to receiving said information by altering the primary timing window so that the primary timing window includes the location, in time, where the signal associated with the terminal was found in the secondary timing window.

13. A base station according to claim 12, wherein the terminal tracking module is configured to increase the size of the primary timing window so that the new primary timing window includes the location, in time, where the signal associated with the terminal was found in the secondary timing window and the location, in time, where a signal associated with the terminal was found in the old primary timing window.

14. A base station according to claim 10 or 11, wherein the terminal tracking module is configured to modify the primary timing window in response to receiving said information by creating a second primary timing window.

15. A base station according to claim 14, wherein the terminal tracking module is configured to continuously search, for some period of time, the first and second primary timing windows for a signal associated with the terminal, wherein the second primary timing window is smaller in size than the secondary timing window but includes the location, in time, where the signal associated with the terminal was found in the secondary timing window.

16. A base station according to any of claims 9 to 15, further including a timing module configured to send a timing alignment value to the terminal in response to a determination that the strength of the signal that was found by searching the secondary timing window exceeds a threshold, wherein the timing alignment value corresponds to a delay associated with that signal.

17. A base station according to any of claims 9 to 16, wherein the secondary searching module is configured to search the secondary timing window less frequently than the tracking module is configured to search the primary timing window.

Ansprüche

1. Verfahren zum Betreiben einer Basisstation (104) zum Versorgen eines mobilen Endgeräts (102), wobei die Basisstation die folgenden Schritte ausführt:

Empfangen eines Signals, das vom mobilen Endgerät (102) gesendet wird;

Durchsuchen eines primären Zeitfensters nach einem Signal, das mit dem mobilen Endgerät verknüpft ist;

Durchsuchen eines sekundären Zeitfensters nach einem Signal, das mit dem mobilen Endgerät verknüpft ist, wobei das sekundäre Zeitfenster größer ist als das primäre Zeitfenster;

Bestimmen der Stärke eines Signals, das mit dem mobilen Endgerät verknüpft ist, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde; und

Bestimmen auf Grundlage der bestimmten Stärke für das Signal, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde, ob das primäre Zeitfenster modifiziert werden soll.

2. Verfahren nach Anspruch 1, des Weiteren umfassend das Modifizieren des primären Zeitfensters als Reaktion auf eine Bestimmung, dass die Stärke des Signals, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde, einen Schwellenwert übersteigt.

3. Verfahren nach Anspruch 2, des Weiteren umfassend das Modifizieren des primären Zeitfensters als Reaktion auf eine Bestimmung, dass die Stärke des Signals, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde, die Stärke eines mit dem mobilen Endgerät verknüpften Signals übersteigt, das beim Durchsuchen des primären Zeitfensters gefunden wurde.

4. Verfahren nach Anspruch 2 oder 3, wobei der Schritt des Modifizierens des primären Zeitfensters das Verändern des primären Zeitfensters umfasst, so dass das primäre Zeitfenster die zeitliche Position enthält, wo das mit dem mobilen Endgerät verknüpfte Signal im sekundären Zeitfenster gefunden wurde.

5. Verfahren nach Anspruch 4, wobei die Größe des primären Zeitfensters erhöht ist, so dass das neue primäre Zeitfenster die zeitliche Position, wo das mit dem mobilen Endgerät verknüpfte Signal im sekundären Zeitfenster gefunden wurde, und die zeitliche Position, wo ein mit dem mobilen Endgerät verknüpftes Signal im alten primären Zeitfenster gefunden wurde, enthält.

6. Verfahren nach Anspruch 2 oder 3, wobei der Schritt des Modifizierens des primären Zeitfensters das Erstellen eines zweiten primären Zeitfensters enthält und das Verfahren des Weiteren das kontinuierliche Durchsuchen, für eine gewisse Zeitperiode, des ersten und zweiten primären Zeitfensters nach einem Signal umfasst, das mit dem mobilen Endgerät verknüpft ist, wobei das zweite primäre Zeitfenster kleiner ist als das sekundäre Zeitfenster, aber die zeitliche Position enthält, wo das mit dem mobilen Endgerät verknüpfte Signal im sekundären Zeitfenster gefunden wurde.

7. Verfahren nach einem der vorangehenden Ansprüche, des Weiteren umfassend:

Senden eines Zeitausrichtungswertes an das mobile Endgerät (102) als Reaktion auf eine Bestimmung, dass die Stärke des Signals, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde, einen Schwellenwert übersteigt, wobei der Zeitausrichtungswert einer mit diesem Signal verknüpften Verzögerung entspricht.

8. Verfahren nach einem der vorangehenden Ansprüche, wobei das sekundäre Zeitfenster weniger häufig durchsucht wird als das primäre Zeitfenster.

9. Basisstation (104), umfassend:

einen Empfänger (304) zum Empfangen von Signalen, die von einem Endgerät (102) gesendet werden;

ein Endgerätverfolgungsmodul, das zum Durchsuchen eines primären Zeitfensters nach einem mit dem Endgerät verknüpften Signal konfiguriert ist;

ein sekundäres Suchmodul, das zum Durchsuchen eines sekundären Zeitfensters nach einem mit dem Endgerät verknüpften Signal konfiguriert ist, wobei das sekundäre Zeitfenster größer ist als das primäre Zeitfenster;

ein Signalstärkenbestimmungsmodul, das zum Bestimmen der Stärke eines Signals konfiguriert ist, das mit dem Endgerät verknüpft ist, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde; und

ein Datenverarbeitungsmodul, das zum Bestimmen auf Grundlage der bestimmten Stärke für das Signal, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde, ob das primäre Zeitfenster modifiziert werden soll, konfiguriert ist.

10. Basisstation nach Anspruch 8, wobei das Endgerätverfolgungsmoduls des Weiteren zum Modifizieren des primären Zeitfensters als Reaktion auf den Empfang von Informationen, die anzeigen, dass die Stärke des Signals, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde, einen Schwellenwert übersteigt, konfiguriert ist.

11. Basisstation nach Anspruch 10, wobei der Schwellenwert ein Wert ist, der die Stärke eines mit dem Endgerät verknüpften Signals darstellt, das beim Durchsuchen des primären Zeitfensters gefunden wurde.

12. Basisstation nach Anspruch 10 oder 11, wobei das Endgerätverfolgungsmodul zum Modifizieren des primären Zeitfensters als Reaktion auf den Empfang der Informationen konfiguriert ist, indem das primäre Zeitfenster so verändert wird, dass das primäre Zeitfenster die zeitliche Position enthält, wo das mit dem Endgerät verknüpfte Signal im sekundären Zeitfenster gefunden wurde.

13. Basisstation nach Anspruch 12, wobei das Endgerätverfolgungsmodul zum Erhöhen der Größe des primären Zeitfensters konfiguriert ist, so dass das neue primäre Zeitfenster die zeitliche Position, wo das mit dem Endgerät verknüpfte Signal im sekundären Zeitfenster gefunden wurde, und die zeitliche Position, wo ein mit dem Endgerät verknüpftes Signal im alten primären Zeitfenster gefunden wurde, enthält.

14. Basisstation nach Anspruch 10 oder 11, wobei das Endgerätverfolgungsmodul zum Modifizieren des primären Zeitfensters als Reaktion auf den Empfang der Informationen konfiguriert ist, indem ein zweites primäres Zeitfenster erstellt wird.

15. Basisstation nach Anspruch 14, wobei das Endgerätverfolgungsmodul zum kontinuierlichen Durchsuchen, über eine gewisse Zeitperiode, des ersten und zweiten primären Zeitfensters nach einem Signal, das mit dem Endgerät verknüpft ist, konfiguriert ist, wobei das zweite primäre Zeitfenster kleiner ist als das sekundäre Zeitfenster, aber die zeitliche Position enthält, an der das mit dem Endgerät verknüpfte Signal im sekundären Zeitfenster gefunden wurde.

16. Basisstation nach einem der Ansprüche 9 bis 15, des Weiteren enthaltend ein Zeitsteuerungsmodul, das zum Senden eines Zeitausrichtungswertes an das Endgerät als Reaktion auf eine Bestimmung, dass die Stärke des Signals, das beim Durchsuchen des sekundären Zeitfensters gefunden wurde, einen Schwellenwert übersteigt, konfiguriert ist, wobei der Zeitausrichtungswert einer mit diesem Signal verknüpften Verzögerung entspricht.

17. Basisstation nach einem der Ansprüche 9 bis 16, wobei das sekundäre Durchsuchungsmodul zum weniger häufigen Durchsuchen des sekundären Zeitfensters konfiguriert ist als das Verfolgungsmodul zum Durchsuchen des primären Zeitfensters konfiguriert ist.

Revendications

1. Procédé de fonctionnement d'une station de base (104) afin de poursuivre un terminal mobile (102), la station de base exécutant les étapes consistant à :

recevoir un signal émis à partir du terminal mobile (102) ;

rechercher un signal associé au terminal mobile dans une fenêtre principale de synchronisation ;

rechercher un signal associé au terminal mobile dans une fenêtre secondaire de synchronisation, la fenêtre secondaire de synchronisation étant plus large que la fenêtre principale de synchronisation ;

déterminer l'intensité d'un signal associé au terminal mobile qui a été trouvé en balayant la fenêtre secondaire de synchronisation ; et

déterminer si la fenêtre principale de synchronisation doit être modifiée en fonction de l'intensité déterminée du signal trouvé en balayant la fenêtre secondaire de synchronisation.

2. Procédé selon la revendication 1, comprenant en outre l'étape consistant à modifier la fenêtre principale de synchronisation s'il a été déterminé que l'intensité du signal trouvé en balayant la fenêtre secondaire de synchronisation dépasse un certain seuil.

3. Procédé selon la revendication 2, comprenant en outre l'étape consistant à modifier la fenêtre principale de synchronisation s'il a été déterminé que l'intensité du signal trouvé en balayant la fenêtre secondaire de synchronisation dépasse l'intensité d'un signal associé au terminal mobile qui a été trouvé en balayant la fenêtre principale de synchronisation.

4. Procédé selon la revendication 2 ou 3, dans lequel l'étape de modification de la fenêtre principale de synchronisation comprend l'étape consistant à modifier la fenêtre principale de synchronisation de telle sorte que la fenêtre principale de synchronisation comprenne la position dans le temps où a été trouvé dans la fenêtre secondaire de synchronisation le signal associé au terminal mobile.

5. Procédé selon la revendication 4, dans lequel la taille de la fenêtre principale de synchronisation est augmentée de telle sorte que la nouvelle fenêtre principale de synchronisation comprenne la position dans le temps où a été trouvé dans la fenêtre secondaire de synchronisation le signal associé au terminal mobile et la position dans le temps où a été trouvé dans l'ancienne fenêtre principale de synchronisation un signal associé au terminal mobile.

6. Procédé selon la revendication 2 ou 3, dans lequel l'étape de modification de la fenêtre principale de synchronisation comprend l'étape consistant à créer une seconde fenêtre principale de synchronisation et dans lequel le procédé comprend l'étape consistant à rechercher de manière continue un signal associé au terminal mobile pendant une certaine période de temps dans la première et la seconde fenêtre principale de synchronisation, dans lequel la seconde fenêtre principale de synchronisation est de taille plus petite que la fenêtre secondaire de synchronisation mais comprend la position dans le temps où a été trouvé dans la fenêtre secondaire de synchronisation le signal associé au terminal mobile.

7. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre l'étape consistant à :

envoyer au terminal mobile (102) une valeur d'alignement dans le temps après qu'il a été déterminé que l'intensité du signal trouvé en balayant la fenêtre secondaire de synchronisation dépasse un certain seuil, la valeur d'alignement dans le temps correspondant à un retard associé à ce signal.

8. Procédé selon l'une quelconque des revendications précédentes, dans lequel la fenêtre secondaire de synchronisation est balayée moins fréquemment que la fenêtre principale de synchronisation.

9. Station de base (104) comprenant :

un récepteur (304), destiné à recevoir un signal émis à partir d'un terminal (102) ;

un module de poursuite de terminaux configuré pour rechercher un signal associé au terminal dans une fenêtre principale de synchronisation ;

un module de recherche secondaire configuré pour rechercher un signal associé au terminal mobile dans une fenêtre secondaire de synchronisation, la fenêtre secondaire de synchronisation étant plus large que la fenêtre principale de synchronisation ;

un module de détermination de l'intensité du signal configuré pour déterminer l'intensité d'un signal associé au terminal qui a été trouvé en balayant la fenêtre secondaire de synchronisation ; et

un module de traitement de données configuré pour déterminer si la fenêtre principale de synchronisation doit être modifiée en fonction de l'intensité déterminée du signal trouvé en balayant la fenêtre secondaire de synchronisation.

10. Station de base selon la revendication 9, dans laquelle le module de poursuite de terminaux est en outre configuré pour modifier la fenêtre principale de synchronisation après réception d'informations indiquant que l'intensité du signal trouvé en balayant la fenêtre secondaire de synchronisation dépasse un certain seuil.

11. Station de base selon la revendication 10, dans laquelle la valeur de seuil est une valeur représentant l'intensité d'un signal associé au terminal qui a été trouvé en balayant la fenêtre principale de synchronisation.

12. Station de base selon la revendication 10 ou 11, dans laquelle le module de poursuite de terminaux est configuré pour modifier la fenêtre principale de synchronisation après réception desdites informations en modifiant la fenêtre principale de synchronisation de telle sorte que la fenêtre principale de synchronisation inclue la position dans le temps où a été trouvé dans la fenêtre secondaire de synchronisation le signal associé au terminal mobile.

13. Station de base selon la revendication 12, dans laquelle le module de poursuite de terminaux est configuré pour augmenter la taille de la fenêtre principale de synchronisation de telle sorte que la nouvelle fenêtre principale de synchronisation comprenne la position dans le temps où a été trouvé dans la fenêtre secondaire de synchronisation le signal associé au terminal mobile et la position dans le temps où a été trouvé dans l'ancienne fenêtre principale de synchronisation un signal associé au terminal mobile.

14. Station de base selon la revendication 10 ou 11, dans laquelle le module de poursuite de terminaux est configuré pour modifier la fenêtre principale de synchronisation après avoir reçu lesdites informations en créant une seconde fenêtre principale de synchronisation.

15. Station de base selon la revendication 14, dans laquelle le module de poursuite de terminaux est configuré pour rechercher de manière continue un signal associé au terminal mobile pendant une certaine période de temps dans la première et la seconde fenêtre principale de synchronisation, dans lequel la seconde fenêtre principale de synchronisation est de taille plus petite que la fenêtre secondaire de synchronisation mais comprend la position dans le temps où a été trouvé dans la fenêtre secondaire de synchronisation le signal associé au terminal mobile.

16. Station de base selon l'une quelconque des revendications 9 à 15, comprenant en outre un module de synchronisation configuré pour envoyer au terminal une valeur d'alignement dans le temps après qu'il a été déterminé que l'intensité du signal trouvé en balayant la fenêtre secondaire de synchronisation dépasse un certain seuil, la valeur d'alignement dans le temps correspondant à un retard associé à ce signal.

17. Station de base selon l'une quelconque des revendications 9 à 16, dans laquelle le module de recherche secondaire est configuré pour balayer la fenêtre secondaire de synchronisation moins fréquemment que le module de poursuite n'est configuré pour balayer la fenêtre principale de synchronisation.

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